This invention relates to a method and apparatus for de-icing the leading edge of an airfoil section of an aircraft and more particularly to an improved method and apparatus which circulates a heated liquid through a conduit extending along the leading edge of the airfoil section of the aircraft to cause de-icing of such leading edge.
As is well known, during certain weather conditions, considerable difficulties have been encountered with the accumulation of ice on airfoil sections of aircraft. In most instances, the ice is formed along the leading edges of the airfoil sections by freezing rain, snow, sleet and other forms of precipitation which occur while flying through saturated air. The ice is retained on the leading edges of the airfoil sections by the forces of the air which pass over and under the airfoil sections and by the adhesive tension between the ice and the material used to form the airfoil sections. The forces of the air passing over and under the airfoil sections constantly dislodge and remove ice which is built up on the thicker mid portions and on the trailing edges of the airfoil sections. Accordingly, as ice builds up along the leading edges of the airfoil sections, the shapes of the wings and tail section may be changed so that they will no longer be able to produce the differential pressures required to sustain the weight of the aircraft in flight.
Many attempts have been made to avoid the accumulation and build up of ice along the leading edges of airfoil sections of aircraft. Among such attempts include the installation of expandible de-icer boots on the leading edges of airfoil sections which crack and dislodge the ice when inflated. Also, porous de-icing fluid distributors have been employed along the leading edges of the airfoil sections to distribute de-icing fluid which melts the ice deposited thereon. U.S. Pat. No. 2,371,269 discloses an aircraft ice preventer which utilizes the hot exhaust gases of the engine propelling the aircraft to melt the ice on the leading edges of the airfoil sections. Heating tubes are disposed within the leading edges of the wings and tail airfoil sections with one end of each tube being connected to the engine exhaust system. Hot gases flow through the heating tubes to heat the leading edges of the airfoil sections and then are discharged to the atmosphere. Difficulties have been encountered with this type de-icer system due to the fact that the exhaust gases are not dense enough to carry and conduct heat along the full length of the airfoil sections of the aircraft. That is, heat from the exhaust gases is rapidly conducted to the portions of the leading edges of the wing and tail sections which are closest to the engine exhaust system while the remaining areas of the leading edges of the airfoil sections receive little or no heat to bring about removal of the ice accumulated thereon. This is especially true since the forces of the air rushing over the discharge valves at the wing tip areas create a negative pressure which causes the cooled exhaust gases to be rapidly discharged through the exhaust valves into the atmosphere before they can conduct heat to the ice accumulated on the leading edges.